In the further development of radar sensor systems in the automotive field, advances in semiconductor technology offer new possibilities of integration. For technological reasons, a clear separation existed in the past between a high-frequency generation and reception, on the one hand, and signal conditioning and signal processing, on the other. It has been known for approximately two generations that silicon-germanium MMICs (monolithic microwave integrated circuit) are used for high-frequency signals, and that processors, DSPs (digital signal processor), FPGAs (field-programmable gate array) and special ASICs (application-specific integrated circuit) for controlling the SiGe MMICs are realized in standard silicon technology (CMOS (complementary metal-oxide semiconductor) or mixed signal), and are therefore also implemented in different modules.
The current state of the art allows for the increasing integration of digital circuit technology in silicon-germanium high-frequency MMICs. This is made possible by the further development of the SiGe process in the direction of the BiCMOS process with SiGe semiconductor junctions. With the aid of the BiCMOS module, digital circuits can be directly integrated together with high-frequency modules, which replaces conventionally employed special ASICs for the control and evaluation of the MMICs. Subject matters of the advanced MMIC integration are essentially an integrated PLL for frequency stabilization and integrated A/D converters, which digitize the baseband signals required for the evaluation. In addition, these digital data are made available to the controller for further processing via a suitable digital interface.
Furthermore, with a view toward highly automated driving, the demands on functional safety according to ISO 26262 are growing. According to this standard, it must be ensured at all times that faults in the MMIC are identified and indicated within the shortest period of time in order to avoid incorrect reactions based on false data. As a rule, each subcomponent in a complex module must be monitored, which involves a considerable amount of time not only in carrying out the monitoring, but in particular also when polling the monitoring result. This time is then lost in the surroundings detection, which restricts the performance of a radar sensor.
In PCT Published Patent Application No. WO 2013/117277 A1, this problem was already addressed by an alarm line, which indicates monitoring that is autonomously taking place in the MMIC to the microcontroller only if a fault case has actually occurred. In such a case, additional monitoring data may be requested from the MMIC in an effort to contain the error.